On-chip excitation and readout architecture for high-density magnetic sensing arrays based on quantum defects

ABSTRACT

A sensing array includes a plurality of pixels, one pixel of which includes: a sensor, the sensor including a first electrode, a second electrode, and an atomic defect site configured to be excited by light of a first frequency; a light source below the sensor and configured to emit light of the first frequency toward the defect site; and a radio frequency (RF) source below the sensor and configured to provide a first voltage to the first electrode, a second voltage to the second electrode, and an RF signal to the sensor, wherein the sensor is configured to sense a magnitude of a physical parameter by generating a photocurrent corresponding to a magnitude of a physical parameter and a differential between the first and second voltages, when excited by the light of the first frequency and affected by the RF signal.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to, and the benefit of, U.S.Provisional Application No. 62/676,443 (“HIGH-DENSITY MAGNETIC FIELDIMAGING ARRAY”), filed on May 25, 2018, and U.S. Provisional ApplicationNo. 62/768,534 (“HIGH-DENSITY MAGNETIC FIELD IMAGING ARRAY”), filed onNov. 16, 2018, the entire contents of which are incorporated herein byreference.

This application is related to a U.S. patent application Ser. No.16/399,649 (“INTEGRATED OPTICAL WAVEGUIDE AND ELECTRONIC ADDRESSING OFQUANTUM DEFECT CENTERS”), filed on Apr. 30, 2019, the entire content ofwhich is incorporated herein by reference.

FIELD

Aspects of the present invention relate to the field of defect-basedsensors and arrays.

BACKGROUND

Recent advances in the field of nanotechnology have led to greatinterest in developing sensing techniques that work at the nanoscale.Research has shown that spin defects in large band gap materials,including diamond and silicon carbide, are capable of operating assensors for electromagnetic fields, mechanical forces, material strain,and high energy particles with nanometer-scale spatial resolution.

The readout mechanism for such defect-based sensors has beenpredominantly based on optical detection of fluorescence. However, theinefficiencies associated with optical readout, including internalreflection losses, significantly limit the signal-to-noise ratiosachievable with this sensing technology. Also, conventional defect-basedsensors often require large table-top optical equipment that have to beproperly aligned.

The above information disclosed in this Background section is only forenhancement of understanding of the invention, and therefore it maycontain information that does not form the prior art that is alreadyknown to a person of ordinary skill in the art.

SUMMARY

Aspects of embodiments of the present invention are directed toward anatomic defect sensor utilizing atomic defects to enable high spatialresolution (sub-micron), high sensitivity, and portable sensors formeasuring magnetic, electric, strain, or temperature fields. In someembodiments, the atomic defects are used as atomic magnetometers capableof measuring and spatially mapping the strength of a magnetic field withhigh precision and at high spatial resolution.

According to some embodiments of the present invention, there isprovided a sensing array including a plurality of pixels, a pixel of theplurality of pixels including: an atomic defect sensor at a first layer,the atomic defect sensor including a first electrode, a secondelectrode, and an atomic defect site configured to be excited by lightof a first frequency; a light source at a second layer below the firstlayer and configured to emit light of the first frequency toward theatomic defect site; and a radio frequency (RF) source at a third layerbelow the second layer and configured to provide a first voltage to thefirst electrode, a second voltage to the second electrode, and an RFsignal to the atomic defect sensor, wherein the atomic defect sensor isconfigured to sense a magnitude of a physical parameter by generating aphotocurrent corresponding to a magnitude of a physical parameter and avoltage differential between the first and second voltages, when excitedby the light of the first frequency and affected by the RF signal.

In some embodiments, the first and second electrodes are electricallycoupled to the RF source through a first via and a second via,respectively, that pass through the second layer.

In some embodiments, the light source includes an optical diffractiongrating configured to receive light of the first frequency from a laserand to focus the light onto the atomic defect site above the lightsource.

In some embodiments, the optical diffraction grating is opticallycoupled to the laser by an optical waveguide.

In some embodiments, the RF source includes: a varactor configured togenerate a tuned Rf signal based on a broadband RF signal; a positivebias tee configured to receive a first voltage and the tuned RF signaland to generate a combined signal based on the first voltage and thetuned RF signal to supply to the first electrode of the atomic defectsensor; and a negative bias tee configured to receive a second voltageand to apply the second voltage to the second electrode of the atomicdefect sensor, the negative bias tee being coupled to a terminationpoint, wherein the first and second voltages establish a voltagedifferential across the atomic defect site.

In some embodiments, the varactor is a variable capacitance diode withan adjustable pass band configured to tune frequencies of the tuned RFsignal to correspond to the magnitude of the physical parameter beingmeasured.

In some embodiments, the pixel further including: an accumulationcapacitor at a fourth layer below the third layer and configured toaccumulate the photocurrent from the atomic defect sensor for readout bya readout control circuitry.

In some embodiments, the negative bias tee is further configured tosupply the photocurrent from the atomic defect sensor to accumulationcapacitor through a readout via.

In some embodiments, the varactor is configured to receive the broadbandRF signal from an RF signal generator through a horizontal transmissionvia at a fifth layer below the fourth layer and a vertical RF via.

In some embodiments, the physical parameter is magnetic field,temperature, or stress.

According to some embodiments of the present invention, there isprovided a sensing array including a plurality of pixels, a pixel of theplurality of pixels including: an atomic defect sensor at a first layer,the atomic defect sensor including a first electrode, a secondelectrode, and an optical waveguide including an atomic defect siteconfigured to be excited by light of a first frequency; and a radiofrequency (RF) source at a second layer below the first layer andconfigured to provide a first voltage to the first electrode, a secondvoltage to the second electrode, and an RF signal to the atomic defectsensor, wherein the atomic defect sensor is configured to sense amagnitude of a physical parameter by generating a photocurrentcorresponding to a magnitude of a physical parameter and a voltagedifferential between the first and second voltages, when excited by thelight of the first frequency and affected by the RF signal.

In some embodiments, the optical waveguide is optically coupled to alaser configured to emit the light of the first frequency, the opticalwaveguide being configured to guide the light of the laser toward theatomic defect site.

In some embodiments, the optical waveguide includes a plurality ofdefect sites including the atomic defect site, the plurality of defectsites corresponding to a row of pixels of the plurality of pixels.

In some embodiments, the atomic defect sensor further includes: a firstdoped fin integrated with the optical waveguide at a first side of theoptical waveguide and electrically coupled to the first electrode; and asecond doped fin integrated with the optical waveguide at a second sideof the optical waveguide and electrically coupled to the secondelectrode, wherein the first doped fin further includes p-type dopingand the second doped fin further includes n-type doping or p-typedoping.

In some embodiments, the first and second electrodes are electricallycoupled to the RF source through a first via and a second via,respectively, the first and second vias being vertical vias.

In some embodiments, the RF source includes: a varactor configured togenerate a tuned Rf signal based on a broadband RF signal; a positivebias tee configured to receive a first voltage and the tuned RF signaland to generate a combined signal based on the first voltage and thetuned RF signal to supply to the first electrode of the atomic defectsensor; and a negative bias tee configured to receive a second voltageand to apply the second voltage to the second electrode of the atomicdefect sensor, the negative bias tee being coupled to a terminationpoint, wherein the first and second voltages establish a voltagedifferential across the atomic defect site.

In some embodiments, the varactor is a variable capacitance diode withan adjustable pass band configured to tune frequencies of the tuned RFsignal to correspond to the magnitude of the physical parameter beingmeasured.

In some embodiments, the pixel further including: an accumulationcapacitor at a third layer below the second layer and configured toaccumulate the photocurrent from the atomic defect sensor for readout bya readout control circuitry, wherein the negative bias tee is furtherconfigured to supply the photocurrent from the atomic defect sensor toaccumulation capacitor through a readout via.

In some embodiments, the varactor is configured to receive the broadbandRF signal from an RF signal generator through a horizontal transmissionvia at a fourth layer below the third layer and a vertical RF via.

In some embodiments, the physical parameter is magnetic field,temperature, or stress.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateexample embodiments of the present invention, and, together with thedescription, serve to explain the principles of the present invention.

FIG. 1A is a cross-sectional view of an atomic defect sensor, accordingto some embodiments of the present invention.

FIG. 1B is a perspective view of the atomic defect sensor, according tosome embodiments of the present invention.

FIG. 1C is a perspective view of the atomic defect sensor, according tosome embodiments of the present invention.

FIG. 2A illustrates an atomic defect sensor, according to someembodiments of the present invention.

FIG. 2B illustrates a one-dimensional sensor array including atomicdefect sensors 200, according to some embodiments of the presentinvention.

FIG. 3A illustrates an exploded view of a two-dimensional sensor array,according to some exemplary embodiments of the present invention.

FIG. 3B illustrates an exploded view of several layers of a pixel of thetwo-dimensional sensor array, according to some exemplary embodiments ofthe present invention.

FIG. 3C illustrates a readout layer and an RF source layer of thetwo-dimensional sensor array, according to some embodiments of thepresent invention.

FIG. 4A illustrates an exploded view of a two-dimensional sensor array400-1, according to some exemplary embodiments of the present invention.

FIG. 4B illustrates an exploded view of several layers of a pixel of thetwo-dimensional sensor array, according to some exemplary embodiments ofthe present invention.

FIG. 5 illustrates a tile arrangement of two-dimensional sensor arrays,according to some embodiments of the present invention.

DETAILED DESCRIPTION

In the following detailed description, only certain example embodimentsof the present invention are shown and described, by way ofillustration. As those skilled in the art would recognize, the inventionmay be embodied in many different forms and should not be construed asbeing limited to the embodiments set forth herein. Descriptions offeatures or aspects within each example embodiment should typically beconsidered as being available for other similar features or aspects inother example embodiments. Like reference numerals designate likeelements throughout the specification.

Embodiments of the present invention utilize atomic defects as sensors(or transducers) as they exhibit high sensitivity to external factors,such as magnetic fields, temperatures, stress, etc. The atomic scale ofsuch sensors enables embodiments of the present invention to be deployedin applications that benefit from very high spatial resolution(sub-micron), high sensitivity, and portable needs for measuringmagnetic, electric, strain, or temperature fields.

Accordingly, some embodiments of the present invention are directed toan architecture for the deployment of atomic defect-based sensors(referred to herein as atomic defect sensors) in large-scale,high-density arrays. In some embodiments, the atomic defects are used asatomic magnetometers capable of measuring and spatially mapping thestrength of a magnetic field with high precision and at high spatialresolution.

One example use case may be monitoring an integrated circuit (IC) as itis running to detect abnormal behavior. In some embodiments, an array ofatomic sensors acts as a real-time magnetic camera, which, for example,allows the detection of currents passing through a circuit in real-time(i.e., by mapping the magnetic fields generated by the currents). Forexample, in a wafer with thousands of chips, an atomic sensor arrayaccording to some embodiments of the present invention may be able toidentify those chips that are not behaving like the other chips, andflag the identified chips as potentially defective.

Other example use cases may be precisely aligning (e.g., at micronscale) machining tools on opposite sides of very large parts, such as anairplane wing during assembly. Further, brain imaging usingmagnetoencephalography (MEG) may leverage the sensing array to helppinpoint locations of signals generated by brain activity.

As noted above, the use case of the present invention are quite varied,and applications range from, for example, material science to the lifesciences.

According to some embodiments, on-chip optical waveguides are utilizedfor excitation of atomic defects (e.g., nitrogen-vacancy defects), andcustomized electronic doping profiles (e.g., P-I-N or P-I-P dopingprofiles) are used to perform electrical read out of sensed information.This allows defects to be addressed optically and read out electricallyfully on-chip, thus enabling a scalable and portable architecture fordeploying such sensors. High-density packaging of these components mayallow for sub-micron pixel sizes in imaging applications. According tosome embodiments, the unique P-I-N/P-I-P intrinsic diamond dopingstructure of the atomic defect sensor overcomes the ohmic lossesassociated with related art device technologies to achieve animprovement in signal-to-noise (SNR) ratio up to a factor of 100 timeslarger than annealed metal contacts.

FIG. 1A is a cross-sectional view of an atomic defect sensor 100,according to some embodiments of the present invention. FIG. 1B is aperspective view of the atomic defect sensor 100-1, according to someembodiments of the present invention. FIG. 1C is a perspective view ofthe atomic defect sensor 100-2, according to some embodiments of thepresent invention.

Referring to FIGS. 1A-1B, according to some embodiments, the atomicdefect sensor 100 includes a substrate (an electrically-insulating,optically transparent substrate) 102 including a large bandgap material,such as diamond, silicon carbide (SiC), and or the like; a defect site104 including one or more atomic defect centers (e.g., atomic-scalequantum defects) 106 within the substrate 102; a pair of electrodes 108a and 108 b on the substrate 102 and overlapping with the defect site104; and a doped region 110 within the substrate 102 and below the pairof electrodes 108 a and 108 b. In embodiments in which the substrate 102includes diamond, the atomic defect centers 106 may includenitrogen-vacancy (NV) color centers, and in embodiments in which thesubstrate 102 includes silicon carbide (SiC), the atomic defect centers106 may include a missing carbon or silicon atom. Each of the NV colorcenters may include a single substitutional nitrogen atom associated toa nearest-neighbor vacancy.

The atomic defect centers 106 may be created using any suitabletechnique known to a person of ordinary skill in the art. For example,NV centers may be created by irradiating a diamond substrate withNitrogen ions, irrigating the substrate with vacancies, and thenannealing the diamond substrate to cause the vacancies to move andbind/link with the Nitrogen atoms to produce NV centers. However,embodiments of the present invention are not limited thereto.

In some embodiments, a first voltage VDD (e.g., a high voltage, e.g., 5V) is applied to the first electrode 108 a and a second voltage (e.g., alow voltage, e.g., 0 V) is applied to the second electrode 108 b. Thecurrent collected by the electrode pair 108 may be measured using acurrent sensor (e.g., an ammeter) 116. In some embodiments, a dopingregion 110 is formed in the substrate 102 below the electrode pair 108,which improves the ohmic contact resistance between the electrode pair108 and the substrate 102, and makes it easier to extract electrons fromthe defect sites 104 and improve readout signal-to-noise ratio (SNR).This may be particularly desired when the substrate 102 is a diamondsubstrate, as diamond may not form a good metal contact (i.e., may havehigh contact resistance). The doping region 110 may include two separatedoping portions, one of which is formed beneath the first electrode 108a and the other of which is formed beneath the second electrode 108 b.The two doping portions may be N-type-N-type, N-type-P-type, orP-type-P-type. For example, in embodiments having a SiC substrate, thedoping region 110 may include separate N-type and P-type dopingportions, and in embodiments having a diamond substrate, the dopingregion 110 may include separate P-type doping portions.

In embodiments that utilize a substrate of SiC, common doping techniquesmay be used to form the doping region 110 below the electrode pair 108.However in embodiments that utilize a diamond substrate, the diamond isgrown with the doped regions.

According to some embodiments, the atomic defect site 104 is configuredto be energetically stimulated by light of a first frequency (which maybe within the green light spectrum in the case of NV defects) when inthe presence of an RF signal, and to generate a photocurrentcorresponding to the magnitude of the physical parameter (e.g., magneticfield) and a voltage differential across the pair of electrodes 108 aand 108 b, which are at opposite sides of the atomic defect site 104. Insome examples, light of the first frequency may include light in therange of about several hundred nanometers. For example, in the case ofNV centers in diamond, the light may range from about 500 nm to about637 nm, and in the case of defect centers in SiC, the light may rangefrom about 750 nm to about 900 nm.

In an atomic defect center 106, an electron, when stimulated to a higherenergy level by light of the first frequency, can return to its groundstate (e.g., ground electron spin state) of ms=0 by emission of a photonof a second frequency (e.g., a red color photon, in the case of NVcenters), which can be detected in optically detected magnetic resonance(ODMR) techniques of the related art. In the presence of an electricfield created by the voltage difference across the first and secondelectrodes 108 a and 108 b, the excited electron may be carried to oneof the electrodes 108 a and 108 b, which can result in a photocurrentthat may be detected by the current sensor. The light of the firstfrequency may be generated by the light source 112, which may be a laserlight source.

In the absence of a magnetic field, applying microwave radiation/RFsignal (via the microwave/RF source 114) of a particular frequency canresult in transitions to a degenerate state (e.g., a degenerate electronspin state). In the example of defects in diamond, the particularfrequency may be about 2.87 GHz, and the degenerate state may bems=+/−1. In the examples of defects in SiC, the particular frequency mayrange from about 70 MHz to about 500 MHz, and the degenerate state maybe ms=+/−3/2.

When the electrons in the degenerate state are exposed to the light ofthe first frequency, the electrons recombine back to the ground state ofms=0, and in the process, produce less of the photons of the secondfrequency. This also leads to a change in photocurrent that may bemeasured by the current sensor. In some examples, the change inphotocurrent may represent a dip or an increase in photocurrent,depending on the type of defect centers 106.

When a magnetic field is present, the Zeeman effect occurs which splitsthe degenerate state level (e.g., ms=+/−1 or ms=+/−3/2) into twodistinct energy levels (e.g., ms=+1 and ms=−1, or ms=+3/2 and ms=−3/2,which can be occupied by the electrons through the microwavestimulation. When excited by light of the first frequency, electrons inthe two split states are elevated to a high energy level and recombineback to ground state, thus producing different photoluminescenceintensities at the two different microwave frequencies. Thus, twomeasurable resonance dips in photoluminescence occur. The sameresonances may be measured as changes in the photocurrent. For example,the photocurrent may drop by about 1% to about 20% at the resonantfrequencies, relative to non-resonance photocurrent. This dip (or“contrast”) observed in the photocurrent may depend on the chargerelaxation rate (or charge cycle rate) of the defects, which may bedependent on the type of the defect. The difference in frequency betweenthe double minima is determined by the energy gap between these twosplit levels (also referred to as a Zeeman shift). The gap itselfdepends on the strength of the magnetic field and, in the case of NVcenters, may be about 28 MHz/mT. Therefore, the strength of the magneticfield may be determined by measuring the frequency difference betweenthe double minima in photocurrent. Accordingly, in some embodiments, theatomic defect center 106 acts as a magnetometer of atomic size withsensitivity to magnetic field in the order of μT.

A desirable aspect of the present invention is the photoelectric gainmechanism, which may lead to high detection efficiency since everyphoton of the light of first frequency has the ability to generate morethan one electron—hole pair. The amount of photocurrent may depend onthe density of the atomic defects centers 106 in the defect site 104,and may be in the picoamp to nanoamp range, according to some examples.

As shown in FIG. 1B, in some embodiments, the pair of electrodes 108 aand 108 b is a pair of interdigital electrodes 108 a-1 and 108 b-1(e.g., comb-like structures fitting into each other). Such anarrangement allows for great trace length around the defect site 104 forcapturing photocurrents generated by the defect site 104 before theyrecombine in the material. As shown in FIG. 1C, in some embodiments, thepair of electrodes 108 a and 108 b may be a pair of rectangular ortrapezoidal electrodes 108 a-2 and 108 b-2 that face each other, andwhich may partially overlap the defect site 104. According to someembodiments, the rectangular or trapezoidal electrodes 108 a-2 and 108b-2 allow for small feature sizes and be well-suited for use inhigh-density arrays. For example, the depth L1 of the atomic defectsensor 100-2 along the first direction D1 and the width L2 of the atomicdefect sensor 100-2 along the second direction D2 may each be about 10μm to about 100 μm. Aside from the electrodes 108 a and 108 b, theatomic defect sensors 100-1 and 100-2 may be same or substantially thesame as the atomic defect sensors 100. As such, a detailed descriptionof atomic defect sensors 100-1 and 100-2 will not be repeated here.

FIG. 2A illustrates an atomic defect sensor 200, according to someembodiments of the present invention.

According to some embodiments, the atomic defect sensor 200 includes anoptical waveguide 202 extending in a first direction D1, a defect site204 within the optical waveguide 202, and a first doped fin 206 a and asecond doped fin 206 b integrated with (e.g., forming a unitary/unifiedbody with) the optical waveguide 202 and extending in a second directionD2 crossing (e.g., perpendicular to) the first direction D1. In someembodiments, the first and second fins 206 a and 206 b are electricallycoupled to first and second sides, respectively, of the opticalwaveguide 202 at a point corresponding to the defect site 204. Forexample, the defect site 204 and the first and second fins 206 a and 206b may be aligned along a same axis. The defect site 204 may be the sameor substantially the same as the defect site 104, and thus, adescription of the defect site 204 will not be repeated here.

The optical waveguide 202 includes intrinsic material, such as diamond,silicon carbide, or the like. According to some embodiments, the firstand second doped fins 206 a and 206 b include (e.g., are formed of) thesame material as the optical waveguide 202, and are doped to enableconduction of electrical current through the atomic defect site 204. Insome examples, the first doped fin 206 a includes P-type material andthe second doped fin 206 b includes N-type material, thus forming aP-I-N junction with the optical waveguide 202. However, embodiments ofthe present invention are not limited thereto, and in some examples, thesecond doped fin 206 b may include P-type material, thus forming a P-I-Pjunction with the optical waveguide 202. The p-type material may includeboron doping (e.g., may be doped with about 1e19/1e20/cm² of boron), andthe n-type material may include dopings of any group V element, such asphosphorous doping. The optical waveguide 202 and the first and secondfins 206 a and 206 b may be co-fabricated (e.g., may be concurrentlyetched from the same diamond substrate). The P-I-N or P-I-P junctionsallow for electrical readout of photo-ionized current from the defectcenters in the defect site 204.

The first doped fin 206 a may be electrically coupled to the first DCvoltage source VDD, and the second doped fin 206 b may be electricallycoupled to the second DC voltage source VSS, which is at a lowerpotential than the first DC voltage source VDD. In some embodiments, afirst electrode 208 a may be coupled between the first DC voltage sourceVDD and the first doped fin 206 a, and a second electrode 208 b may becoupled between the second DC voltage source VSS and the second dopedfin 206 b. The first and second electrodes 208 a and 208 b may be planarcontacts that cover a bottom side (as shown) or a top side of the firstand second fins 206 a and 206 b to increase or maximize contact surfacetherebetween and, in effect, reduce or minimize contact resistance.However, embodiments of the present invention are not limited thereto,and the first and second electrodes 208 a and 208 b may bethree-dimensional and cover part of all of the front, back, and/orleft/right sides of the first and second fins 206 a and 206 b as well.

The use of the doped first and second fins 206 a and 206 b as integratedohmic contacts significantly improves the electrical readoutsensitivity, and the thin optical waveguide 202 allows the atomic defectsensor 200 to achieve high charge mobility (e.g., in diamond).

A current sensor 210, which is electrically connected between the firstand second DC voltage sources VDD and VSS, senses the current passingthrough the defect site 204. The current sensor 210 may include anon-chip current amplifier and/or current-to-voltage converter.

The optical waveguide 202 guides the light (e.g., green light) from thelight source 212 (e.g., a laser or photodiode) toward the defect site204, which resides within the optical waveguide 202. The light interactswith, and excites, unpaired electrons of the atomic defect centers(e.g., atomic-scale quantum defects). These stimulated electrons maythen be swept away by the potential difference generated across thedefect site by the first and second fins 206 a and 206 b, which are atdifferent potentials.

As described above with respect to FIGS. 1A-1B, the magnetic fieldpresent at the location of the defect site 204 may be measured via theZeeman interaction with magnetic sublevels ms=±1 of energy levels in theground state spin structure of the charged defect centers (e.g., thenegatively charged nitrogen vacancy defects) in the defect site 204. Anexternal magnetic field, which the atomic defect sensor 200 seeks tomeasure, splits the degeneracy between the ms=±1 states by an amount setby the gyromagnetic ratio γ≈2.8 MHz/G, which is the change in electronicenergy due to interactions with an incident magnetic field. According tosome embodiments, the atomic defect sensor 200 determines the strengthof the external magnetic field by measuring this energy splitting usingelectron spin resonance (ESR), which utilizes spin-dependentphotoionization of carriers (e.g., unpaired electrons) from the defectcenters in the defect site 204. The long spin coherence time of theatomic defect sensor 200, which may be as long as 1 ms at roomtemperature, allows for narrow ESR linewidths and consequently highmagnetic field sensitivity.

Unlike optically detected magnetic resonance (ODMR), which exhibit lowfield sensitivity (measured in units of nT/√Hz) due to low photoncollection efficiencies of about 1%, the electrically detected magneticresonance (EDMR) utilized by the atomic defect sensor 200 provides asensitivity that is limited by current shot noise instead of photon shotnoise. Because of an effectively higher collection efficiency forelectrons versus photons, due to the p-i-n doping structure, the atomicdefect sensor 200 may provide higher signal-to-noise ratios than systemsadopting the ODMR technique. In some examples, the atomic defect sensor200 may provide a SNR in the range of about 10 pT/√Hz to about 100pT/√Hz. Because of the photon confinement effect of the opticalwaveguide 202, the photonic structure of the atomic defect sensor 200minimizes or substantially reduces the optical excitation of the dopedfirst and second fins 206 a and 206 b, which could otherwise negativelyimpact SNR. Further, the integration of the on-chip current sensor 210with the atomic defect sensor 200 (e.g., direct integration of thecurrent sensor 210 with the diamond substrate from which the atomicdefect sensor 200 is etched) also improves SNR relative to systems inwhich the current sensor or amplifier are not integrated with the atomicdefect sensor.

According to some examples, the lower bound for the dynamic range of theatomic defect sensor 200 may be set by the linewidth of the ESRresonances, which depends on the spin coherence time of the defectcenters used in the defect site 204. In some examples, the minimumdetectable field using a single defect center may be about 30 nT toabout 300 nT, for long coherence times in the 100 μs to about 1000 μsrange. In other examples using an ensemble of defect centers, theminimum detectable field may be even lower, for example, several hundredpT for coherence times in the 100 μs to about 1000 μs range. The upperbound of the dynamic range may be limited by energy level anti-crossingsin the defect center electronic structure, which may become significantabove about 50 mT.

In some embodiments, the upper limit to the bandwidth of the atomicdefect sensor 200 corresponds to (e.g., is set by) the cycling time ofthe electrons under optical excitation, which may be dominated by theapproximately 200 ns lifetime of the metastable state populated duringthe relaxation process. Thus, according to some examples, the bandwidthof the atomic defect sensor 200 may be up to a few MHz. In contrast,bandwidth limits of the related art ODMR techniques are dominated byphoton counting statistics from the relatively weak optical signal ofthe defect centers measured in a confocal topology, which may limit suchtechniques to sub-kHz bandwidths to allow enough time to collectsufficient signal. The atomic defect sensor 200, according to someembodiments, exceeds these bandwidth limitations owing to the muchhigher SNR achievable over optical techniques to approach MHz bandwidthperformance.

FIG. 2B illustrates a one-dimensional sensor array 300 including atomicdefect sensors 200, according to some embodiments of the presentinvention.

According to some embodiments, a plurality of atomic defect sensors 200may share a common optical waveguide 202 to form a one-dimensionalsensor array 300. In some embodiments, the one-dimensional sensor array300 is formed by etching the optical waveguide and a plurality of firstfins 206 a-1 to 206 a-n (where n is an integer greater than two) andsecond fins 206 b-1 to 206 b-n out of a same substrate (e.g., diamond orSiC), doping the fins to form P-type and/or N-type regions, andpatterning a plurality of defect sites 204-1 to 204-n to correspond tothe crossing points of the corresponding fins and the optical waveguide202. In such an array, a single light source may concurrently (e.g.,simultaneously) excite all defect sites 204-1 to 204-n along the sharedoptical waveguide.

The defect sites 204-1 to 204-n may be patterned at regular intervals.For example, the separation between each pair of doped fins 206 may beabout 220 nm to about 2 μm. The optical waveguide 202 may itself behundreds of micrometer long or much longer, depending on theapplication. However, the power loss in the optical waveguide 202 (whichmay be about 0.5 db/cm in a diamond waveguide) may limit how long thewaveguide can be in practice. The sensing volume of the atomic defectsensors 200, which may be the volume of the defect centers 106, may beas small as 1 nm³, in some examples.

The design of the atomic defect sensor 200 is particularly amenable toarrays. For example, while FIG. 2B illustrates only a one-dimensionalsensor array 300, several one-dimensional sensor arrays may be formedside-by-side to produce a two-dimensional sensor array. Similarly, amultitude of atomic defect sensors 100 may be distributed along a planeto form a two-dimensional sensor array. Such two-dimensional sensorarray may be capable of imaging the spatial variation of an externalmagnetic field along a two-dimensional plane. The resolution of such amagnetic image is determined by the spacing between adjacent defectsites. According to some examples, the minimum spacing between pixelsmay be limited by the requirement for photocurrent generated by eachdefect site 204-i (i being an integer from 1 to n) to only be collectedby the fins 206 a-i/206 b-i corresponding to the defect site 204-i. Thismay be a function of the lateral diffusion of electrons in the waveguide202 (which may be made of diamond) as well as the uniformity of theelectric field applied to the waveguide 202 that directs excited chargecarriers to their respective drain contacts (e.g., electrode 208 a/b).

Referring to FIGS. 2A-2B, a single defect site 204 may only provide ameasurement of the magnetic field along its symmetry axis. However,utilizing an ensemble of defect centers 106 with different crystalorientations may provide access to magnetic fields along other axes. Ameasurement of the Zeeman splitting provides the magnitude of the fieldalong the defect axis, not the sign of the field, and any additionalmeasurements from other crystallographic orientations may also onlyprovide field magnitude information along each crystallographicorientation. However, with a two-dimensional array of atomic defectsensors 100/200, additional vector information can be inferred fromstitching the measurements of adjacent sensors together and applying theconstraint that the divergence of the magnetic field is zero. In someexamples, vector magnetometry can be achieved at each defect site104/204 due to the ensemble of defects centers 106 at each defect site104/204, which may be partitioned into at least four distinct classesaccording to the symmetry axis in the crystal lattice. The four classesof defects centers 106 at each site 104/204 are sensitive to differentphysical directions, and therefore produce a unique configuration forthe four pairs of Zeeman-split lines. By inverting the uniqueconfiguration, it may be possible to deduce the vector orientation ofthe magnetic field incident on the defect site 104/204.

The size of the sensor array may be tuned to obtain a desiredresolution/SNR tradeoff for a given application. For example, SNR may beimproved, at the expense of reducing spatial resolution, by changing theeffective sensor size and wiring multiple sensors 100/200 in parallel.

According to embodiments of the present invention, optical excitationvia the waveguide 202 (e.g., the on-chip waveguide) allows for targetedexcitation of the intrinsic region while reducing or minimizing exposureof doped regions to optical excitation, which would contribute excessbackground photocurrent and reduce SNR.

Further, the electrical readout of the atomic defect sensor 100/200eliminates the needs for photon collection optics (such as objectlenses, which are required in ODMR systems) and makes the system robustto temperature drift and shock, as no fine optical alignment isnecessary for defect excitation or fluorescence collection. Electricalreadout according to the embodiments of the present invention alsoeliminates the need to mechanically stabilize a photo-detector'sposition relative to the sensor, and circumvents the technicallychallenging task of extracting optical photons from a high refractiveindex material (such as diamond), while also providing a more efficientmethod for extracting spin information. Additionally, vibrations may notaffect the spatial resolution of the array, as that is determined byelectrical leads and layout, not by optical focusing and control.Furthermore, unlike the ODMR solutions of the related art, which requiretable-top components and setup, the integrated sensor/sensor arrayaccording to some embodiments of the present invention allows for aportable design that can be battery operated (assuming the batteryprovides sufficient RF power to perform ESR and sufficient laser powerto defect excitation). Embodiments of the present invention that utilizea diamond substrate 102 or waveguide 202 are also able to endure extremetemperature and pressure environments.

FIG. 3A illustrates an exploded view of a two-dimensional sensor array400, according to some exemplary embodiments of the present invention.

Referring to FIG. 3A, according to some embodiments, the variouscomponents of the two-dimensional sensor array 400 may be organized intoa number of layers (or stacks) including a quantum defect layer 402 anda photonic layer 404.

According to some embodiments, the quantum defect layer 402 includes aplurality of atomic defect sensors 410, which may be the same as theatomic defect sensors 100-1 (described with respect to FIG. 1A-1B)and/or atomic defect sensors 100-2 (described with respect to FIGS. 1Aand 1C).

In some embodiments, the photonic layer 404 includes a plurality oflight sources 412 that correspond to (e.g., have a one-to-onecorrespondence with) the plurality of atomic defect sensors 410 at thequantum defect layer 402. The light sources 412 may be similar to thelight sources 112 and 212 (described with respect to FIGS. 1A-1C and2A-2B). In some embodiments, the light sources 412 include opticaldiffraction gratings that receive light from optical waveguides 413 anddirect (e.g., focus) the received light onto the corresponding defectsites 104 of the corresponding atomic defect sensors 410 located at thequantum defect layer 402. A row of light sources 412 (e.g., along thesecond direction D2) may be optically coupled to, and received lightfrom, the same optical waveguides 413.

A desirable effect of utilizing this stacked array structure is that,the defect centers 106 can be formed in one material (e.g., one that ismost suitable for the defect centers 106), and the light source 412 canbe at a layer having a material with desirable optical characteristics.This allows for intended optimization of the two layers.

According to some embodiments, the two-dimensional sensor array 400 alsoincludes a microelectronics layer 406, which includes a plurality ofradio frequency (RF) sources 414 that correspond to (e.g., have aone-to-one correspondence with) the plurality of atomic defect sensors410 at the quantum defect layer 402. The RF sources may be the same asthe RF sources 114 and 214 described with respect to FIGS. 1A-1C and2A-2B and are each configured to perform microwave tuning the RF signalsupplied to a corresponding atomic defect sensor 410.

In some embodiments, the two-dimensional sensor array 400 furtherincludes a readout layer 408 for capturing the data sensed by the atomicdefect sensors 410, and an RF source layer 409 for providing RF signalsto the pixels Pxl.

While the different layers/stacks of the two-dimensional sensor array400 (e.g., the quantum defect layer 402, the photonic layer 404, themicroelectronics layer 406, the readout layer 408, and the RF sourcelayer 409) are illustrated as separated layers for illustrationpurposes, the operational two-dimensional sensor array 400 involvescompact integration and interlinking of all these layers/stacks.

The photonic layer 404 may be coupled to a laser 420 (e.g., an on-chip,integrated laser) that supplies light of a particular frequency (e.g.,green light, in the case of diamond NV centers) to the opticalwaveguides 413 that are optically coupled to the optical diffractiongratings 412. The light generated by the laser 420 may be continuouslyapplied or may be pulsed for consecutive readout sequences. For example,when a readout sequence is performed, excitation light is applied,followed by the RF signal, and finally by current readout. This sequencemay be repeated continuously to extract information from the defectsites 104 in the pixels Pxl. While FIG. 3A illustrates a single lasersource, embodiments of the present invention are not limited thereto,and several lasers may be utilized, each of which provides optical lightto one or more optical waveguides 413. The microelectronics layer 406may be coupled to electronic circuits 422 that include microwaveelectronics for providing a broadband RF signal to the RF sources 414.The electronic circuits 422 may further include a switching network formultiplexed addressing of the atomic defect sensors 410 of thetwo-dimensional sensor array 400. As illustrated in FIG. 3A, thetwo-dimensional sensor array 400 may be divided into a plurality ofsensing cells/pixels Pxl(i,j) (where i and j are positive integers),each of which represents a vertical stack of elements that is capable ofsensing the magnitude of the magnetic field at the location of thesensing cell/pixel Pxl(i,j). For example, each sensing cell/pixelPxl(i,j) (henceforth simply referred to as pixel Pxl(i,j)) includes anatomic defect sensor 410, an optical diffraction grating 412, RF source414, as well as other corresponding elements from the layers below thequantum defect layer 402.

FIG. 3B illustrates an exploded view of several layers of a pixelPxl(i,j) of the two-dimensional sensor array 400, according to someexemplary embodiments of the present invention.

In referring to FIG. 3B, while the atomic defect sensor 410 illustratedin FIG. 3B is the same as the atomic defect sensor 100-2 illustrated inFIG. 1C, embodiments of the present invention are not limited thereto.For example, the atomic defect sensor 410 may be the same as the atomicdefect sensor 100-1 illustrated in FIG. 1B, which has the interdigitalelectrodes.

According to some embodiments, the electrodes 430 a and 430 b of theatomic defect sensor 410 at the quantum stack 402 may be electricallyconnected to the RF source 414 at the microelectronics layer 406 by apair of vias (e.g., vertical vias) 432 a and 432 b that pass through thephotonic layer 404.

In some embodiments, the RF source 414 applies not just the DC biasingvoltages (i.e., the first voltage VDD and second voltage VSS) but alsothe RF signal RFout(i,j) to the atomic defect sensor 410 through thepair of vias 432 a and 432 b. In such embodiments, the RF source 414includes a varactor 434, which is configured to generate a tuned Rfsignal RFout(i,j) based on a broadband RF signal RFin. The RF source 414combines the RF signal with the first voltage VDD using a positive biastee 436 a, which includes a resistor-capacitor (RC) circuit that addsthe tuned Rf signal RFout(i,j) to the first voltage VDD and applies theresultant combined signal VDD+RFout(i,j) to the first via 432 a. Thus,combined signal VDD+RFout(i,j) is applied to the first electrode 430 aof the atomic defect sensor 410. The second electrode 430 b of theatomic defect sensor 410 is electrically connected to a negative biastee 436 b at the microelectronics layer 406 through the second via 432b. The negative bias tee 436 b may be coupled to a termination pointthat acts as an RF dump. In some examples, the termination point may bea 50 ohm resistor or a comparable impedance matched resistor on chip.

According to some embodiments, the varactor 434 is a variablecapacitance diode, that effectively acts as a tunable filter (e.g., atunable low-pass filter) with an adjustable pass band that canindividually tune the frequency of the generated Rf signal RFout(i,j) toclosely correspond to the magnitude of the magnetic field being sensedby the particular atomic defect sensor 410 of the same pixel Pxl(i,j).The varactor 434 may do so using an input broadband RF signal RFin thatmay be common to all of the pixels Pxl. The tuning of the varactor 434may be achieved by adjusting a gate voltage Vgate of the varactor, whichis supplied by the electronic circuits 422. The supply and groundvoltages Vsupply and Vground used to operate the varactor 434, as wellas the first supply voltage VDD may also be provided by the electroniccircuits 422.

While the embodiments illustrated in FIG. 3B provide individual controlover sweeping frequencies of the Rf signal RFout(i,j) applied to each ofthe pixels Pxl(i,j), embodiments of the present invention are notlimited thereto. For examples, antenna lines, which are electricallycoupled to the electronic circuits 422, may be placed at the quantumdefect layer 402 and may emit the same broadband RF signal (e.g., thebroadband RF signal RFin) to all of the pixels Pxl. As described below,doing so may be desirable when sensing a fast varying magnetic field.However, when the magnetic field is slow-varying or static, havingindividual control over sweep frequency may provide higher bandwidth andgreater dynamic range relative to a case in which the same broadband RFsignal is applied to all of the pixels Pxl.

This is due to the fact that for the atomic defect sensors 410 to sensethe strength of the magnetic field, the frequency of the RF signal atthe location of the defect site 104 has to be resonant with the spintransitions of the defect centers 106. The RF frequency may be sweptacross a wide range of frequencies to ensure that the two resonant tones(or one of the two tones) of the defect centers 106 of each atomicdefect sensors 410 is swept over, but this will result in a lowbandwidth as sweeping over portions of the frequency band not atresonance with the spin transitions doesn't yield any information aboutthe magnetic field and only wastes sweep time. However, if the magneticfield doesn't change very fast (or, e.g., is static), each RF source 414may track/follow (via the electronic circuits 422) the sensed magneticfield at the corresponding pixel Pxl(i,j) so that the sweep range can bereduced to cover the one or two resonant tones. Because the average ofthe frequencies f1 and f2 of the two resonant tones is always a constantvalue (e.g., about 2.8 GHz for diamond), and the frequencies f1 and f2shift/move symmetrically about the average frequency, only one of thetwo tones is tracked, according to some embodiments of the presentinvention. In some examples, tone tracking may be achieved by a lock-intechnique whereby a circuit is utilized to achieve a control feedbackloop so that any shift the transitions can be followed at a rateproportional to the inverse of the total integration time per sequence.

While the embodiments illustrated in FIG. 3B provide both of the biasingvoltages VDD and VSS and the Rf signal RFout(i,j) from themicroelectronics layer 406, embodiments of the present invention are notlimited thereto. For example, the DC biasing voltages (i.e., the firstvoltage VDD and second voltage VSS) may be supplied by conductive linesresiding at the quantum defect layer 402, which are shared by some of orall of the pixels Pxl. However, providing the combined signalsVDD+RFout(i,j) and VSS+RFout(i,j) through the pair of vias 432 a and 432b allows for greater integration and potentially smaller pixel sizes(and hence greater sensing resolution), by freeing up crucial space atthe quantum defect layer 402 that would have otherwise been taken byconductive lines.

Referring again to FIG. 3B, when the light from the optical diffractiongrating 412 excites the defect centers at the atomic defect sensor 410while the combined signal RFij+VDD is applied to the first electrode 430a, unpaired carriers at the defect site 106 are collected by the secondelectrode 430 b, which is at the second DC voltage VSS (e.g., ground).The resulting photocurrent passes through the second via 432 b to thenegative bias tee 436 b, which is coupled to a termination point. Thephotocurrent is then directed by a readout via 438 to the readout layer408 for collection and measurement.

FIG. 3C illustrates the readout layer 408 and the RF source layer 409 ofthe two-dimensional sensor array 400, according to some embodiments ofthe present invention.

Referring to FIG. 3C, in some embodiments, the readout layer 408includes a plurality of interconnected charge accumulation capacitors442, each of which corresponds to an atomic defect sensor 410, and thusa pixel Pxl. Each charge accumulation capacitor 442 is electricallycoupled to a corresponding RF source 414 of the same pixel Pxl throughthe readout via 438, and is able to receive and store the charge fromthe photocurrent of the corresponding atomic defect sensor 410. Thestored charge is indicative of the strength of the magnetic field at thelocation of the atomic defect sensor 410.

In some examples, the charge accumulation capacitors 442 of theplurality of pixels/cells together make up a frame transfer CCD imagearray that can be readout by a readout control circuit 444 in atime-multiplexed manner by shifting/moving the stored charges betweenneighboring charge accumulation capacitors 442 one at a time. In someexamples, readout control circuit 444 may control the last chargeaccumulation capacitor 442 to supply its charge into a charge amplifier,which then converts the charge into a voltage. By repeating thisprocess, the readout control circuit 444 converts the entire contents ofthe array of charge accumulation capacitors 442 to a sequence ofvoltages. These voltages are then sampled, digitized, and stored inmemory for further processing to determine the strength of the magneticfield at each pixel Pxl.

Referring still to FIG. 3C, in some embodiments, the RF source layer 409includes a broadband RF signal generator 446 that is electricallycoupled to the varactor 434 of each pixel Pxl via a plurality of RF vias440 and a plurality of transmission vias 448.

FIG. 4A illustrates an exploded view of a two-dimensional sensor array400-1, according to some exemplary embodiments of the present invention.FIG. 4B illustrates an exploded view of several layers of a pixelPxl′(i,j) of the two-dimensional sensor array 400-1, according to someexemplary embodiments of the present invention.

Referring to FIGS. 4A-4B, according to some embodiments, the sensorarray 400-1 is substantially the same (e.g., structurally andfunctionally) as the sensor array 400 (described with respect to FIGS.3A-3C), with the exception that the sensor array 400-1 does not utilizea separate photonic layer 404 and that the quantum defect layer 402-1 isdifferent from the quantum defect layer 402 (described above withrespect to FIGS. 3A-3B). The operation and structure of themicroelectronics layer 406, the readout layer 408, and the RF sourcelayer 409 of the sensor array 400-1 are the same or substantially thesame as those of the sensor array 400. As such, a description of commonor shared elements will not be repeated here.

The sensor array 400-1 does not require a separate photonic layer 404 asoptical routing is integrated into the quantum defect layer 402-1.According to some embodiments, the quantum defect layer 402-1 includes atwo-dimensional array of atomic defect sensors 410-1, which are the sameas the atomic defect sensors 200 (described with respect to FIG. 2A).The atomic defect sensors 410-1 are arranged to form a plurality ofparallel one-dimensional sensor arrays 300 (described with reference toFIG. 2B). As described with reference to FIG. 2B, each one-dimensionalsensor array 300 includes a series of atomic defect sensors 410-1/200sharing a common optical waveguide 202. In some embodiments, a singlelaser (e.g., an in-chip integrated laser) 420 is utilized to coupleoptical power into the parallel optical waveguides 202. However,embodiments of the present invention are not limited thereto, andseveral lasers may be utilized, each of which provides optical light toone or more optical waveguides 202.

Referring to FIG. 4B, each atomic defect sensor 410-1 corresponds to asensing pixel PXI′. In some embodiments, the first and second doped fins206 a and 206 b of the atomic defect sensor 410-1 are electricallycoupled to the first and second electrodes 430 a and 430 b,respectively, which are in turn electrically connected to themicroelectronics layer 406 through the pair of vias 432 a and 432 b. Asdescribed above with respect to FIGS. 1A-1C and 2A, the atomic defectsensor 410-1 is configured to sense a magnitude of a physicalparameter/quantity (e.g., magnetic field strength, temperature, etc.) bygenerating a photocurrent corresponding to a magnitude of a physicalparameter/quantity and a voltage differential between the first anddoped fins 206 a and 206 b, when excited by light of the a particularfrequency (e.g., green light) and affected by the RF signal.

A desirable effect of utilizing the atomic defect sensors 410-1 is thatby placing the defect centers 106 within the optical waveguide 202 andintegrating the doped fins 206 a and 206 b with the waveguide 202, theatomic defect sensors 410-1 allow for high level of integration andsimplify the structure of the sensed array 400-1.

Further, the design of the sensor array 400/400-1 permit high sensingresolution and sensitivity. Each atomic defect sensors 410/410-1 maypotentially offer nanometer or micrometer resolution as the size of theatomic defect site 104 of each sensor may be about 0.5 μm to about 10μm, in some examples. However, the resolution of the sensor array400/400-1 (i.e., the pixel size) may be defined by the spacing betweenadjacent atomic defect sensors 410/410-1 (of adjacent pixels), which maybe about 1 μm to about 100 μm, in some examples. Such high pixel densitycan yield array resolutions that are in the micrometer range.

The sensitivity and resolution may increase the closer the atomic defectsensors 410/410-1 of the array 400/400-1 get to the test object/device(e.g., a conductor passing current within a test circuit). For example,if the array 400/400-1 is far from the test object/device, the magneticfield readings can get blurry/fuzzy. According to some embodiments, theatomic defect centers 106 within atomic defect sensors 410/410-1 areformed at the surface or at a shallow depth below the surface of thesubstrate 102. For example, NV centers may be formed within a 15 nmdepth from the surface of a diamond surface. Because the atomic defectsensors 410/410-1 are at the top-most layer of the array 400/400-1, theshallow depth of the atomic defect centers 106 allows for the atomicdefect sensors 410/410-1 to get within nanometers of the testobject/device, which substantially improves the sensitivity andresolution of the array 400/400-1.

Thus, by utilizing the array 400/400-1, wide-field imaging magnetometerscan be implemented which have high resolution and sensitivity.

According to embodiments of the present invention, the sensor array400/400-1 and its constituent atomic defect sensors 410/410-1 canmeasure the intensity of the magnetic field without the need forcalibration. This is due to the fact that the magnetic field strength isdeduced at the sensed locations (e.g., at the pixels Pxl) via frequencydetection, and multiplying the frequency by physical constants that areall fixed. This greatly simplifies the operation of a magnetic fielddetector utilizing the sensor array 400/400-1.

While in FIGS. 3A, 3C, and 4A, the readout layer 408 has beenillustrated as being above the RF source layer 409, embodiments of thepresent invention are not limited thereto. For example, the verticalposition of the readout layer 408 and the RF source layer 409 may beswitched.

Referring to FIGS. 3A and 4A, according to some embodiments, theeffective pixel size of the array 400/400-1 may be reconfigured on thefly by averaging together the signals measured from a subset of adjacentpixels Pxl/Pxl′.

FIG. 5 illustrates a tile arrangement 500 of arrays 400/400-1 accordingto some embodiments of the present invention.

Referring to FIG. 5, each sensor array 400/400-1 may, in practice, belimited in size by the size of a semiconductor wafer, which may be about400 mm to about 800 mm in diameter. However, larger sensors of arbitrarysize and shape may be formed by arranging together any number of sensorarrays 400/400-1, which may also be referred to as tiles when placed inan arrangement 500.

While some of the embodiments of the present invention have beendescribed as sensing the magnitude of a magnetic field, embodiments ofthe present invention are not limited thereto. For example, the atomicdefect sensors, according to some embodiments, can be used to sensetemperature, stress/strain, and/or electric field. For example,temperature affects the average frequency of the resonant tones f1 andf2 discussed with respect to FIG. 3B. Thus, by tracking the change inthe average of two tones (i.e., the center frequency), one may sensechanges in temperature. Further, strain and electric fields may causethe two tones to move asymmetrically with respect to the centerfrequency. Thus, by measuring this asymmetry, the atomic defect sensoror sensor array can measure strain and/or electric fields.

Accordingly, embodiments of the present invention leverage thesensitivity of atomic defects in solids, such as the nitrogen-vacancycenter in diamond, in a pixelated array enabling a compact and robustsolution for addressing and manipulating high densities of defect-basedsensors, which are effective at sensing electromagnetic fields,mechanical forces, and high-energy particles with spatial resolutiondown to nanometers. The use of atomic defect centers, according toembodiments of the present invention, allows high magnetic fieldsensitivity and calibration-free performance to be realized in a compactand robust solid-state architecture.

It will be understood that, although the terms “first,” “second,”“third,” etc., may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are used to distinguish one element, component,region, layer, or section from another element, component, region,layer, or section. Thus, a first element, component, region, layer, orsection discussed below could be termed a second element, component,region, layer, or section, without departing from the spirit and scopeof the inventive concept.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of the inventive concept.As used herein, the singular forms “a” and “an” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “include,”“including,” “comprises,” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list. Further, the use of“may” when describing embodiments of the inventive concept refers to“one or more embodiments of the present invention.”

It will be understood that when an element is referred to as being“connected to” or “coupled to” another element, it can be directlyconnected to or coupled to the other element, or one or more interveningelements may be present. When an element is referred to as being“directly connected to,” or “directly coupled to,” another element,there are no intervening elements present.

As used herein, the terms “substantially,” “about,” and similar termsare used as terms of approximation and not as terms of degree, and areintended to account for the inherent variations in measured orcalculated values that would be recognized by those of ordinary skill inthe art.

As used herein, the terms “use,” “using,” and “used” may be consideredsynonymous with the terms “utilize,” “utilizing,” and “utilized,”respectively.

Also, any numerical range recited herein is intended to include allsub-ranges of the same numerical precision subsumed within the recitedrange. For example, a range of “1.0 to 10.0” is intended to include allsubranges between (and including) the recited minimum value of 1.0 andthe recited maximum value of 10.0, that is, having a minimum value equalto or greater than 1.0 and a maximum value equal to or less than 10.0,such as, for example, 2.4 to 7.6. Any maximum numerical limitationrecited herein is intended to include all lower numerical limitationssubsumed therein and any minimum numerical limitation recited in thisspecification is intended to include all higher numerical limitationssubsumed therein. Accordingly, Applicant reserves the right to amendthis specification, including the claims, to expressly recite anysub-range subsumed within the ranges expressly recited herein. All suchranges are intended to be inherently described in this specification.

The electronic circuits and/or any other relevant devices or componentsaccording to embodiments of the present invention described herein maybe implemented utilizing any suitable hardware, firmware (e.g. anapplication-specific integrated circuit), software, or a suitablecombination of software, firmware, and hardware. For example, thevarious components of the electronic circuit may be formed on oneintegrated circuit (IC) chip or on separate IC chips. Further, thevarious components of the electronic circuit may be implemented on aflexible printed circuit film, a tape carrier package (TCP), a printedcircuit board (PCB), or formed on a same substrate. Further, the variouscomponents of the electronic circuit may be a process or thread, runningon one or more processors, in one or more computing devices, executingcomputer program instructions and interacting with other systemcomponents for performing the various functionalities described herein.The computer program instructions are stored in a memory which may beimplemented in a computing device using a standard memory device, suchas, for example, a random access memory (RAM). The computer programinstructions may also be stored in other non-transitory computerreadable media such as, for example, a CD-ROM, flash drive, or the like.Also, a person of skill in the art should recognize that thefunctionality of various computing devices may be combined or integratedinto a single computing device, or the functionality of a particularcomputing device may be distributed across one or more other computingdevices without departing from the scope of the exemplary embodiments ofthe present invention.

While this invention has been described in detail with particularreferences to illustrative embodiments thereof, the embodimentsdescribed herein are not intended to be exhaustive or to limit the scopeof the invention to the exact forms disclosed. Persons skilled in theart and technology to which this invention pertains will appreciate thatalterations and changes in the described structures and methods ofassembly and operation can be practiced without meaningfully departingfrom the principles, spirit, and scope of this invention, as set forthin the following claims and equivalents thereof.

What is claimed is:
 1. A sensing array comprising a plurality of pixels,a pixel of the plurality of pixels comprising: an atomic defect sensorat a first layer of the pixel, the atomic defect sensor comprising afirst electrode, a second electrode, and an atomic defect siteconfigured to be excited by light of a first frequency; a light sourceat a second layer of the pixel below the first layer and configured toemit light of the first frequency toward the atomic defect site; and aradio frequency (RF) source at a third layer of the pixel below thefirst layer and configured to provide a first voltage to the firstelectrode, a second voltage to the second electrode, and an RF signal tothe atomic defect sensor, the first, second, and third layers beingphysically stacked on one another, wherein the atomic defect sensor isconfigured to sense a magnitude of a physical parameter by detecting,via the first and second electrodes, a photocurrent generated at theatomic defect site in response to the atomic defect site being excitedby the light of the first frequency and affected by the RF signal, thephotocurrent corresponding to the magnitude of the physical parameterand a voltage differential between the first and second voltages.
 2. Thesensing array of claim 1, wherein the first and second electrodes areelectrically coupled to the RF source through a first via and a secondvia, respectively, that pass through the second layer.
 3. The sensingarray of claim 1, wherein the light source comprises an opticaldiffraction grating configured to receive light of the first frequencyfrom a laser and to focus the light onto the atomic defect site abovethe light source.
 4. The sensing array of claim 3, wherein the opticaldiffraction grating is optically coupled to the laser by an opticalwaveguide.
 5. The sensing array of claim 1, wherein the RF sourcecomprises: a varactor configured to generate a tuned Rf signal based ona broadband RF signal; a positive bias tee configured to receive a firstvoltage and the tuned RF signal and to generate a combined signal basedon the first voltage and the tuned RF signal to supply to the firstelectrode of the atomic defect sensor; and a negative bias teeconfigured to receive a second voltage and to apply the second voltageto the second electrode of the atomic defect sensor, the negative biastee being coupled to a termination point, wherein the first and secondvoltages establish a voltage differential across the atomic defect site.6. The sensing array of claim 5, wherein the varactor is a variablecapacitance diode with an adjustable pass band configured to tunefrequencies of the tuned RF signal to correspond to the magnitude of thephysical parameter being measured.
 7. The sensing array of claim 5, thepixel further comprising: an accumulation capacitor at a fourth layerbelow the third layer and configured to accumulate the photocurrent fromthe atomic defect sensor for readout by a readout control circuitry. 8.The sensing array of claim 7, wherein the negative bias tee is furtherconfigured to supply the photocurrent from the atomic defect sensor toaccumulation capacitor through a readout via.
 9. The sensing array ofclaim 7, wherein the varactor is configured to receive the broadband RFsignal from an RF signal generator through a horizontal transmission viaat a fifth layer below the fourth layer and a vertical RF via.
 10. Thesensing array of claim 1, wherein the physical parameter is magneticfield, temperature, or stress.
 11. A sensing array comprising aplurality of pixels, a pixel of the plurality of pixels comprising: anatomic defect sensor at a first layer of the pixel, the atomic defectsensor comprising a first electrode, a second electrode, and an opticalwaveguide comprising an atomic defect site configured to be excited bylight of a first frequency; and a radio frequency (RF) source at asecond layer of the pixel below the first layer and configured toprovide a first voltage to the first electrode, a second voltage to thesecond electrode, and an RF signal to the atomic defect sensor, thefirst and second layers being physically stacked on one another, whereinthe atomic defect sensor is configured to sense a magnitude of aphysical parameter by detecting, via the first and second electrodes, aphotocurrent generated at the atomic defect site in response to theatomic defect site being excited by the light of the first frequency andaffected by the RF signal, the photocurrent corresponding to themagnitude of the physical parameter and a voltage differential betweenthe first and second voltages.
 12. The sensing array of claim 11,wherein the optical waveguide is optically coupled to a laser configuredto emit the light of the first frequency, the optical waveguide beingconfigured to guide the light of the laser toward the atomic defectsite.
 13. The sensing array of claim 11, wherein the optical waveguidecomprises a plurality of defect sites comprising the atomic defect site,the plurality of defect sites corresponding to a row of pixels of theplurality of pixels.
 14. The sensing array of claim 11, wherein theatomic defect sensor further comprises: a first doped fin integratedwith the optical waveguide at a first side of the optical waveguide andelectrically coupled to the first electrode; and a second doped finintegrated with the optical waveguide at a second side of the opticalwaveguide and electrically coupled to the second electrode, wherein thefirst doped fin further comprises p-type doping and the second doped finfurther comprises n-type doping or p-type doping.
 15. The sensing arrayof claim 11, wherein the first and second electrodes are electricallycoupled to the RF source through a first via and a second via,respectively, the first and second vias being vertical vias.
 16. Thesensing array of claim 11, wherein the RF source comprises: a varactorconfigured to generate a tuned Rf signal based on a broadband RF signal;a positive bias tee configured to receive a first voltage and the tunedRF signal and to generate a combined signal based on the first voltageand the tuned RF signal to supply to the first electrode of the atomicdefect sensor; and a negative bias tee configured to receive a secondvoltage and to apply the second voltage to the second electrode of theatomic defect sensor, the negative bias tee being coupled to atermination point, wherein the first and second voltages establish avoltage differential across the atomic defect site.
 17. The sensingarray of claim 16, wherein the varactor is a variable capacitance diodewith an adjustable pass band configured to tune frequencies of the tunedRF signal to correspond to the magnitude of the physical parameter beingmeasured.
 18. The sensing array of claim 16, the pixel furthercomprising: an accumulation capacitor at a third layer below the secondlayer and configured to accumulate the photocurrent from the atomicdefect sensor for readout by a readout control circuitry, wherein thenegative bias tee is further configured to supply the photocurrent fromthe atomic defect sensor to accumulation capacitor through a readoutvia.
 19. The sensing array of claim 18, wherein the varactor isconfigured to receive the broadband RF signal from an RF signalgenerator through a horizontal transmission via at a fourth layer belowthe third layer and a vertical RF via.
 20. The sensing array of claim11, wherein the physical parameter is magnetic field, temperature, orstress.